Overnight Breakfast Casserole You Bake Straight From Cold

Ingredients

• 8 cups day-old sourdough cubes (560 g)
• 2 cups whole milk (480 g)
• 1 1/2 cups shredded cheddar (170 g)
• 10 large eggs (500 g)
• 1 medium yellow onion, diced (160 g)
• 1 teaspoon dry mustard (3 g)
• 2 cups chopped baby spinach (60 g)
• 1 1/4 teaspoons fine salt (7 g)
• 1 tablespoon olive oil (14 g)
• 12 ounces cooked breakfast sausage, crumbled (340 g)

Instructions

1. Prepare. Cook onion in oil until soft. Add sausage and spinach, then continue until the spinach is wilted and the skillet looks dry. Spread sourdough in a greased metal dish and distribute the sausage mixture and cheddar between the cubes. Keep the components loose enough for custard to pass through the gaps.
2. Assemble. Whisk eggs, milk, dry mustard, salt, and pepper until completely blended. Pour slowly over the dish, working from edges to center. Press the bread once, release it, and cover. Refrigerate for 8 hours. Before baking, confirm the bread looks hydrated and no watery vegetable liquid has collected around the perimeter.
3. Bake. Uncover and move the cold metal dish directly into a 350°F (175°C) oven. Bake for 45 to 50 minutes. The edges should rise slightly away from the sides, and the center should hold a gentle set when nudged. A thin knife inserted into the middle should show tender crumbs without liquid egg.
4. Finish. Leave the casserole undisturbed briefly before cutting 8 squares. Run a flexible knife around the perimeter, then lift portions with a broad spatula so the soaked bread and savory filling remain layered. Scatter a few scallion slices over the top. Avoid covering the hot pan, which can make the upper bread soft.

Notes

• Choose a metal dish for baking directly from cold. Cook the filling until the skillet is dry, use day-old sourdough, and allow eight hours for hydration. The center is ready when set but still tender.
• Refrigerate for up to 4 days. Reheat one portion for 60 seconds, then check before adding short bursts.

Nutrition Facts